1. Field of the Invention
The present invention relates to an electronic apparatus having a function of communication, which is capable of transferring and/or receiving various data to other electronic apparatus such as personal computers and word processors.
2. Description of the Prior Art
In recent, various kinds of electronic apparatus such as electronic note books, personal computers and word processors are on the market which are capable of storing and displaying personal schedule data, phone number data including names, address and phone numbers, name card data bearing a company name in addition to phone number data and free data of memorandums, and are capable of displaying these stored data in need. Each of these electronic apparatus has an internal memory and some of them have data-communication function for transferring and/or receiving data to other apparatus electrically connected therewith.
Application of the communication function to such small sized electronic apparatus as electronic timepieces may encounter various difficulties in a power voltage and a clock frequency. For example, in a conventional electronic wrist watch, a frequency of its crystal oscillator is 32,768 (2.sup.15)Hz and therefore a time counting signal of 1 Hz is obtained by dividing the frequency 32,768 Hz by 15.
In general, transferring speeds of data-communication, for instance, the transferring speeds specified in the RS-232-C Interface Standard are 300, 600, 1200, 2400, 4800, 9600 and 19200 [bps], which numerals are obtained from an expression 300.times.2.sup.n. Reference signals which are in synchronism with the above transferring speeds are needed for data communication. Even though a signal of 32,768 Hz is divided, however, it is very hard to obtain a reference signal which is synchronism with the data transferring speed with a high precision. Accordingly, an oscillator for data communication is necessary in addition to the crystal oscillator used in an electronic wrist watch to obtain a reference signal of a high precision, which is disadvantageous in assembling a small sized electronic apparatus.
Further, another transferring speed expressed by 75.times.2.sup.n is used for data communication but when for example data is received and stored in a memory, a clock signal of a frequency which is higher than the transferring speed must be used or a much longer time is required for processing data. If the above clock signal of a high frequency is employed for processing data within a short time, a current consumption is increased, resulting in a defect which shortens a battery life in a small sized electronic apparatus which is driven with a battery.
Particularly in an electronic apparatus having communication function, a random access memory (RAM) of a much capacity is employed for storing a number of externally supplied data but this kind of RAM usually needs much current consumption to access data at a high speed. As a result, voltage drop of the battery is occurred during operation, inviting malfunction of electronic circuits or defective operation of a communication system.